fix: pass startup warnings to app as prop (#342)

packages/cli/src/utils/startupWarnings.ts

@@ -0,0 +1,40 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import fs from 'fs/promises';
+import os from 'os';
+import { join as pathJoin } from 'node:path';
+import { getErrorMessage } from '@gemini-code/server';
+
+const warningsFilePath = pathJoin(os.tmpdir(), 'gemini-code-cli-warnings.txt');
+
+export async function getStartupWarnings(): Promise<string[]> {
+  try {
+    await fs.access(warningsFilePath); // Check if file exists
+    const warningsContent = await fs.readFile(warningsFilePath, 'utf-8');
+    const warnings = warningsContent
+      .split('\n')
+      .filter((line) => line.trim() !== '');
+    try {
+      await fs.unlink(warningsFilePath);
+    } catch {
+      warnings.push('Warning: Could not delete temporary warnings file.');
+    }
+    return warnings;
+  } catch (err: unknown) {
+    // If fs.access throws, it means the file doesn't exist or is not accessible.
+    // This is not an error in the context of fetching warnings, so return empty.
+    // Only return an error message if it's not a "file not found" type error.
+    // However, the original logic returned an error message for any fs.existsSync failure.
+    // To maintain closer parity while making it async, we'll check the error code.
+    // ENOENT is "Error NO ENTry" (file not found).
+    if (err instanceof Error && 'code' in err && err.code === 'ENOENT') {
+      return []; // File not found, no warnings to return.
+    }
+    // For other errors (permissions, etc.), return the error message.
+    return [`Error checking/reading warnings file: ${getErrorMessage(err)}`];
+  }
+}